Northstar Center

Summary

Northstar Center is a three-building complex consisting of two
high-rise office buildings and the seventeen-story, twenty-four-hour
Crown Plaza Hotel, built atop a six-floor parking garage. Building
tenants are extremely diverse, consisting of lawyers, banks, shoe
stores and a variety of other businesses.

Challenge

Beginning with only a few tenants per floor, Northstar Center’s
tenant list grew larger and more diverse. Along with the different
tenants, came a variety of work hours, with some businesses working
standard weekday hours and others requiring weekend personnel. The two
aging chillers in the building did not have enough capacity to keep up
with the increasing heat load, and building owners were challenged to
keep different parts of the building cool to accommodate work
schedules. In addition, Northstar Center was faced with new Department
of Natural Resources (DNR) environmental regulations, which required
the center to remove itself from its current well water system.
Northstar Center sought to increase its chiller capacity and to
accommodate the individual needs of its tenants, while helping to
improve the environment for the surrounding community.

Solution

Investigating chiller options, the Northstar operations manager met
with Trane engineers to discuss the capacity challenges of cooling its
two office buildings. Taking into account the differences of the
buildings and the varying ages of the equipment, Trane developed
solutions to answer Northstar’s capacity and zone cooling needs.

Increasing efficiency and reliability Northstar’s aging chiller was replaced with two Trane 800-ton
CenTraVac™ centrifugal chillers. With the fewest moving parts in the
industry,--the CenTraVac chillers are reliable and efficient. “We
replaced our 1 kW/ton chiller with one that is .50 kW/ton. It’s
amazing what it can do,” said Mark Erickson, Northstar Center
operations manager.

Trane centrifugal chillers are also
among the quietest in the industry. “And, if you go down to our
chiller room now, the only thing you hear are the pumps. With the old
chillers, you couldn’t even talk,” Erickson added.

Meeting individual tenant needs A plan was developed to address individual tenant needs. Rather
than cooling the entire building for occupants on one floor, the low
pressure CenTraVac chiller can be turned down to about 10 percent to
run for partial capacity. “We have a core loop where we cool air for
things that run 24-hours a day. Because of that, we had to keep our
water a little cooler. Trane worked hand-in-hand with our engineering
company to develop a solution that was the most efficient,” said
Erickson.

“It’s nice that I can run just one floor,”
Erickson added. “In the past I had to run the whole building just to
keep the load even to keep the chiller from surging."

Improving the environment The new chiller replaces Northstar’s old well water pump, which
required chemicals to treat the water before it was run through the
chiller. “There were a lot of things going in the water and down the
drain,” said Erickson. “The new chiller is way more environmentally
friendly.”

The CenTraVac centrifugal chiller also has the
lowest total refrigerant emissions rate in the industry, and comes
with a five-year leak tight warranty. Ensuring tenant comfort Controls
with easy-to-navigate touch screens and displays allow Northstar
engineers to monitor the equipment and make adjustments as necessary.
“You can go down there and look at the pressures, scroll through it,
everything. We do a daily log, but we don’t even have to do that log,
because it logs itself,” commented Erickson.

Results

Replacing its aging chiller with two Trane CenTraVac centrifugal
chillers has reduced Northstar Center’s electrical consumption nearly
50 percent, while significantly increasing cooling capacity. “Today is
a very warm day and we’re running one chiller,” said Erickson. “Two
cooling towers, but one chiller, and we’re doing just fine.”

The new chiller has also increased tenant satisfaction. “When I
would get the complaints in the past, there was nothing I could
do," stated Erickson. "Now, if for some reason we didn’t
start up right away, I could actually catch up. I have enough capacity
that I could turn on both chillers and cool the building down
fast.”

The reliability of the new chillers also provides
peace-of-mind for facility managers. “It’s one less thing to have to
worry about," said Erickson. "And there are plenty of other
things to worry about.”

About Northstar Center

As its tenants became more diverse and work hours varied, Northstar
Center sought to accommodate the individual comfort needs of its
building occupants.